Study On Removal Of Sulfur From Coal Sludge By Microwave-Chemical Method

Coal washing can improve the quality of coal from the source and is an important way to strengthen the clean utilization of coal.Because washing raw coal will produce a large amount of slime,improving the comprehensive utilization level of slime has become a highly concerned problem in the current form.At present,the first choice for the resource utilization of coal slime is to burn into the furnace for power generation.However,with the increase of high sulfur coal mining,the output of high sulfur coal slime increases significantly.A large amount of sulfurcontaining gas is produced in the combustion process of high sulfur slime,which not only increases the desulfurization cost,but also makes the problems of high-temperature corrosion in furnace and low-temperature corrosion in tail flue more and more serious.Therefore,reducing the sulfur content before slime combustion is of great significance to the safe and economic operation of the boiler.In this paper,microwave combined with chemical additives was used to remove sulfur from coal slime.The desulfurization effects of potassium hydroxide and acetic acid hydrogen peroxide under different microwave power and irradiation time were studied.For the test coal samples with the best removal effect,the surface morphology changes of coal slime samples before and after desulfurization reaction were observed by scanning electron microscope;With the help of XRD,XPS,FTIR and other test methods,the content of inorganic minerals,the occurrence form of organic sulfur and the migration law of sulfur-containing functional groups on the surface of coal slime before and after desulfurization are analyzed,and the reaction mechanism of desulfurization is explored;The influence of microwave desulfurization on the basic properties of coal slime is analyzed.The main conclusions are as follows:1.The ash content of the selected high sulfur slime is 51.19%,and the total sulfur reaches5.57%.The inorganic sulfur content is high,mainly pyrite.The content of thiophene sulfur in organic sulfur is the most,followed by sulfoxide sulfur,and the content of sulfone sulfur,mercaptan and sulfide sulfur is low.2.The sulfur content in coal slime was removed by microwave direct irradiation,and the removal rate was 7.47% under 500 W power and 4 min time.Potassium hydroxide was added for desulfurization under microwave irradiation to explore the effects of solid-liquid ratio,microwave power,irradiation time and potassium hydroxide solution concentration on the removal of sulfur in coal slime.The optimal results of each factor were as follows: solid-liquid ratio of 1:3,microwave power of 300 W,irradiation time of 4 min,potassium hydroxide solution concentration of 300 g/L,and the removal rate of total sulfur in coal slime was 40.8%.The pyrite content in inorganic sulfur in coal slime was significantly reduced,and the removal rates of sulfoxide sulfur and sulfone sulfur in organic sulfur were high,which were 21.53% and17.68%,respectively.3.The coal slurry desulfurization was carried out by the method of microwave combined with oxidation additives.The effects of volume ratio of acetic acid and hydrogen peroxide,solid-liquid ratio,microwave power and irradiation time on the desulfurization rate of coal slurry were investigated by single factor variable experiment.The optimal conditions for each factor were obtained as follows: volume ratio of acetic acid and hydrogen peroxide 1:1,solidliquid ratio 1:3,microwave power 500 W,and irradiation time 3 min.Under the optimal conditions,the removal efficiency was 43.93%.Pyrite in coal slime decreased significantly,and low-valent organic sulfur transformed to high-valent state under oxidation.Sulfonyl sulfur increased by 84.57% after reaction,and thiophene sulfur had the best desulfurization effect,with the removal rate of 33.99%.4.Infrared analysis shows that there are no new surface functional groups in the coal slime after desulfurization,indicating that the overall chemical structure of the coal slime has not changed,and the microwave chemical desulfurization has little effect on the basic properties of the coal slime.When potassium hydroxide and acetic acid hydrogen peroxide were added respectively for desulfurization under microwave irradiation,the ash content of coal slime decreased by 12.27% and 12.43% respectively,and the calorific value increased by 16.46% and17.90% respectively;After desulfurization reaction,the surface of coal slime is rough,the pore structure increases,the ignition temperature decreases from 484℃ to 435℃ and 445℃respectively,and the corresponding temperature of maximum weight loss rate decreases from560℃ to 522℃ and 546℃ respectively.The reduction of ash content and the increase of pore are conducive to oxygen absorption combustion of coal slime and increase the calorific value.